In spine surgery, lateral access approaches are increasingly used to deliver interbody fusion cages to the lumbar spine. These lateral approaches are gaining in popularity because they minimize posterior and/or anterior tissue damage, as well as reduce operating room time and associated blood loss, and infection risk. Conventional lateral approaches include the following: Direct Lateral (transpsoas entry parallel cranially and caudally with the disc space, or retract the psoas); Anterior-Lateral (anterior to the psoas parallel to the disc space); and Superior/Inferior Lateral (non-parallel lateral access to the disc space). See instruments A-C in FIGS. 1-5.
The use of multiple lateral approaches has required the development of a trialing system for each approach, thus increasing the number of surgical instruments and overall procedure cost. Specifically-angled trials limit the surgical approaches to the single specific angle of the trial.
Currently, no conventional trial system allows for determination of the angle of the implanted trial following its satisfactory placement and imaging.
US Patent Publication No. 2008-0077241 (Nguyen) discloses a method of preparing a pair of adjacent vertebral endplates, involving a surgical instrument having a pivoting distal removable insert, a proximal handle portion, a body portion, and a linkage member positioned between the insert and the proximal handle portion, the insert having a first angular position relative to the body. A leading end of the insert may be placed in a first position between two adjacent vertebral endplates and moved to a second position between the adjacent vertebral endplates by impacting the proximal end portion of the surgical instrument. The insert may be pivoted to a second angular position relative to the body portion by rotating the handle about the body portion and may lock the second angular position of the distal insert. The insert may be moved to a third position between the adjacent vertebral endplates by impacting the proximal end portion of the surgical instrument.
US Patent Publication No. 2008-0065082 (Chang) discloses instruments and methods for inserting a rasp into an intervertebral space of a spine and using the rasp to decorticate the adjacent vertebra. More particularly, one embodiment provides an instrument that actively changes the angle of the rasp relative to the instrument. The delivery instrument may use a gear portion to articulate the rasp. A second gear on the rasp may mate with a corresponding gear on the instrument. As the instrument gear rotates relative to the instrument, the instrument gear drives the rasp gear, thereby rotating the rasp to decorticate the vertebra. Trial inserts and methods are also provided to determine an appropriate size of a rasp for decortication.
US Patent Publication No. 2008-0140085 (Gately) discloses a method to insert a spinal implant into a vertebral space, the method including the steps of: grasping the implant with a distal end of an implant insertion tool; holding a proximal end of the implant insertion tool and inserting the implant toward the vertebral space; and manipulating the proximal end to apply a yaw movement to the implant while the implant is attached to the tool and in the vertebral space.
Adjustable TLIF implant inserters are limited in angulation to the axial plane for posterior approach surgeries. These devices do not measure the amount of angulation instilled in the trial. Therefore, there remains a need for adjustable trials that allow for flexion of angles of insertion and measurement of the insertion angle for a lateral trial.